I found no straightforward set of rules for printing in a loose painterly way with carborundum, and Holly our teacher had no great experience of it, so I decided to roll up my sleeves even further and do a few trials. This was to give myself somewhere to start, at least rather than just mucking about almost blindfold.
We kept seeing references to heavy acrylic gel medium as the binder, and also PVA, but nothing definitive, or really in depth. So, I took two grades of carborundum: a medium and a coarse, PVA, some Liquitex Heavy Body * which I had bought when we were working on collagraphs, a spoon, and some tubs, and started stirring. I mixed up four pots' worth as my starting point. Then I prepared two perspex plates. On one I brushed a large numeral with each of the mixtures from the correspondingly numbered tub, with a few stabbed brush marks underneath. On the other plate I used a small sponge roller (the 'throwaway' type you can pick up in art/craft shops) to make a 'solid' area out of which I cleaned a numeral, again corresponding with the mix.
So far, so interesting, even at this stage.
Then I inked them up with black etching ink, and printed them on two pieces of dampened BKF Rives paper, one after the other so that I had the immediate ghost.
First mix is one part medium carborundum to two parts PVA glue. I found it horrible trying to carve out the numeral 1 out of this mix. It was not happy giving any precise marks.
Second mix is one part coarse carborundum to two parts PVA glue. This mixture was even more difficult to control than 1, and as you can see there is no numeral because a whole 'flake' lifted off when I tried any removal. I learned also that the mixtures will devour ink, but be almost impossible to wipe back. Indeed with this mix the wiping back removed the mix also, leaving the pristine perspex. Holly suggested that as I liked the possible effects of this mix that I should consider using it on card to present a firmer grip, and then seal that as for a normal collagraph.
The third mix behaves much more like acrylic paint. It consists of one part medium carborundum, one part PVA, and one part Liquitex Heavy Body. The numeral 3 was easy to carve out with a drypoint tool, and this encouraged me to start considering ways of using this as viable - especially as it has not dried out in my little tub (with lid - originally containing mackerel pate!).
Mix number four consists of one part course carborundum to one part OVA, and one part Liquitex Heavy Body. It also behaves like acrylic paint, but with fewer and larger lumps in unpredictable distribution (unless, I suppose you become meticulous about where you put the agglomerations of large carborundum bits). I like the way that the brush marks are more prominent. I did not make a clean job of carving out the numeral, but that's my fault. On the other hand, the dried rolled mix is not as easy to carve into as mix 3 because of the uneven distribution of larger elements.
As you can see, I cut these up and stuck them into my printmaking notebook. The next experiment was to paint a layer of mix three onto a perspex sheet, then carve out of it with an etching tool, and see what happens to that as a plate. I'm sloshing about with nascent printing skills, but it's bringing more interesting possibilities for picture making into focus.
* The reason why I went for Liquitex when we were making collagraphs was that when I lived in the USA and painted with acrylics Liquitex was the make available at my nearest art store. I had noticed then that they did mixes with interesting elements like sand, but had never had reason to use it then. This stayed in my mind, and popped up when I needed something to make a collagraphic plate. The Heavy Body I discovered on the website when I was looking for the sand stuff.